Field of Invention
The present disclosure relates to a light driving circuit. More particularly, the present disclosure relates to a light driving circuit for driving a plurality of light emitting diode strings.
Description of Related Art
Light emitting diodes (LEDs), having the advantages of high durability, long life, low power consumption together with not containing harmful substances such as mercury, have gradually replaced the traditional bulbs or halogen lamps in lighting market today. When a light emitting diode serves as a light source, a plurality of light emitting diode strings are usually utilized. In addition to that, a driving circuit independently controlling the light emitting diode strings is added to achieve uniform light source or light color regulation.
Traditionally, a light driving circuit for driving a plurality of light emitting diode strings comprises a plurality of buck converters operating independently to respectively drive the light emitting diode strings. FIG. 1 depicts a schematic diagram of a light driving circuit 100 according to the prior art. As shown in FIG. 1, a light driving circuit 100 comprises a power conversion unit 10, a first illuminant unit 11, a second illuminant unit 12, a first buck conversion unit 13, and a second buck conversion unit 14. The first illuminant unit 11 comprises a first light emitting diode string 111 and a first capacitor C. The first capacitor C is connected in parallel with the first light emitting diode string 111. The second illuminant unit 12 comprises a second light emitting diode string 121 and a second capacitor C. The second capacitor C is connected in parallel with the second light emitting diode string 121. The first buck conversion unit 13 comprises a first controller 131. The second buck conversion unit 14 comprises a second controller 141. The first buck conversion unit 13 and the second buck conversion unit 14 are respectively connected to the first illuminant unit 11 and the second illuminant unit 12. In addition, the first buck conversion unit 13 and the second buck conversion unit 14 control currents for driving the first illuminant unit 11 and the second illuminant unit 12 through the first controller 131 and the second controller 141, respectively.
Take the first illuminant unit 11 for example, the power conversion unit 10 is configured for receiving an input voltage Vin and converting the input voltage Vin into an output voltage Vout that is configured for driving the first illuminant unit 11 and the second illuminant unit 12. When a switch S is turned on, a diode D is reverse biased. At this time, the first illuminant unit 11 is driven by the output voltage Vout to generate a current flowing through an inductor L, the switch S, and a resistor R and energy is stored in the inductor L. When the switch S is turned off, the current flows through the diode D and the first illuminant unit 11 because the current in the inductor L cannot change suddenly so that freewheeling is achieved.
In order to drive each of the illuminant units, a buck converter and a control circuit need to be disposed correspondingly in the prior art light driving circuit (for example: when the driving circuit needs to drive three illuminant units, three independent buck converters and three independent control circuits are required to allow each of the illuminant units to be driven). As a result, when the number of the illuminant units is increased, the structure of the light driving circuit becomes more complex, which in turn increases the manufacturing cost of the light driving circuit.
For the forgoing reason, there is a need for solving the above-mentioned problem by providing a light driving circuit.